This invention relates to printing plates and benders therefor, and in particular, to a bender for manufacturing printing plates where the plates are adapted for self-locking onto the plate cylinder of a press apparatus.
Offset printing presses, for example, employ cylinders having thin, metal plates attached to them. The plates, usually of aluminum or other material or metal alloy, have an image to be printed deposited on them by photographic processes. The plates ordinarily are wrapped around the plate cylinders of the presses when they are in use to effect an imprinting. After bending, the plates are wrapped around the periphery of the plate cylinder of the offset press by attaching a leading edge of the plate to one edge defining a first axial groove in the cylinder and thereafter wrapping the plate around the cylinder until the trailing edge of the plate enters the groove at an opposite second edge defining a second axial groove in the cylinder. Conventionally, two plates are required to cover the periphery of the cylinder. In the past, the plates have been held on the cylinders by "fingers" which engage the end edges of the plates. More recently, the plate bends themselves have been employed to effect attachment. For example, a co-pending application by Signorelli et al, Ser. No. 880,459, filed Feb. 23, 1978, discloses a metal printing plate having a reverse bend formed in it. The reverse bend permits the plate to snap on and lock onto the printing cylinder of the offset device so that the plate is juxtapositioned the cylinder along the entire plate area between the leading edge of the plate and a reverse bend part of the trailing edge of the plate. This construction has enabled considerably thinner plates to be manufactured and used than previously possible. Thinner plates have resulted in a substantial material cost savings. The plate construction itself results in less down time of the offset presses, caused, for example, by rupture of the plate during use.
The invention disclosed hereinafter provides a plate bender for forming the plate described in the above-referenced co-pending application. The plate bender may be manufactured as a independent new construction. In the alternative, the components required for forming the reverse bend may be manufactured and sold as a conversion kit for converting plate benders presently available in the art. For example, one prevalent plate bender for forming printing plates is shown and described in the U.S. patent to Gregoire, U.S. Pat. No. 3,733,872, issued May 22, 1973. General features of plate benders not specifically forming a part of the invention disclosed hereinafter are intended to incorporated by reference to the Gregoire patent.
One of the objects of this invention is to provide a plate bender capable of efficiently forming a reverse bend on at least one end of a printing plate.
Another object of this invention is to provide a low cost plate bender for forming a reverse bend on at least one end of a printing plate.
Another object of this invention is to provide structure for converting prior art benders into devices capable of forming a reverse bend on at least one end of a printing plate.
Other objects of this invention will be apparent to those skilled in the art in light of the following description and accompanying drawings.